1. Field of the Invention
The present invention relates to a passive coherent location (PCL) system and method, and more particularly to a PCL system and method for use in moving target surveillance sensors.
2. Description of Related Art
A number of conventional radar systems have particularly high life-cycle costs due to the initial cost of the radar system and the maintenance cost of the radar system. Furthermore, because conventional radar systems typically broadcast electromagnetic signals, a regulated activity, extensive regulatory procurement and compliance costs are associated with operating current radar systems.
Additionally, extensive physical, regulatory, and economic disincentives prevent transporting such systems on a temporary or mobile basis. For example, transporting a current radar system to a special event such as the Olympics, a fireworks display, a construction site, a residence, and the like would pose numerous disincentives, including the assessment of environmental impact proper licensing from various regulatory agencies and the costs associated with moving the electromagnetic signal transmitter.
Accordingly, the present invention is directed to a PCL system and method that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a PCL system that provides enhanced airspace awareness around a predetermined location for lower total life cycle cost than the related art.
An object of the present invention is to provide a PCL system that provides enhanced airspace awareness around a predetermined location using ambient transmissions from at least one uncontrolled transmitter.
An object of the present invention is to provide a PCL system that provides enhanced airspace awareness around a predetermined location based primarily upon frequency change of arrival information derived from ambient transmissions from at least one uncontrolled transmitter.
Another object of the present invention is to provide a PCL system that provides enhanced airspace awareness for a predetermined location, such as an airport, using ambient transmissions from at least one uncontrolled transmitter, wherein the initial position information is determined from frequency-difference-of-arrival, time-difference-of-arrival, and angle-of-arrival information from the ambient transmissions.
An object of the present invention is to provide a PCL system that provides enhanced airspace awareness around a predetermined location as well as enhanced ground-traffic awareness within the predetermined location using ambient transmissions from at least one uncontrolled transmitter.
Another object of the present invention is to provide a mobile radar system that provides enhanced airspace awareness during a predetermined event using ambient transmissions from at least one uncontrolled transmitter.
Yet another object of the present invention is to provide a system and method for selecting a subset of ambient transmission signals from a plurality of ambient transmission signals based on a set of predetermined criteria.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure and method particularly pointed out in the written description and claims hereof as well as the appended drawings.
In one embodiment, a PCL system receives transmissions from a plurality of uncontrolled transmitters. In a preferred embodiment, the uncontrolled transmitters may include radio and television broadcast stations. Additionally, the PCL system may use signals from transmitters operated by operationally independent entities. The signals from uncontrolled transmitters may be used independently or in conjunction with signals from transmitters operated by the organization controlling the PCL system.
In one embodiment, a PCL system includes an antenna subsystem, a coherent receiver subsystem, a front-end processing subsystem, a back-end processing subsystem, and an output device. Each of these subsystems is connected by a communication link, which may be a system bus, a network connection, a wireless network connection, or other type of communication link.
In one embodiment, the present invention is used to monitor the airspace of a predetermined location using ambient transmissions from at least one uncontrolled transmitter. In a preferred embodiment, ambient transmissions are scattered by an object and received by a PCL system. These scattered transmissions are compared with a reference transmission that is received directly from the uncontrolled transmitter to the PCL system. In particular, the frequency-difference-of-arrival between the scattered transmission and the reference transmission is determined, which allows the radial velocity of the object to be determined. The present invention may be used in conjunction with or in lieu of a conventional radar system.
In one embodiment, the present invention is used to monitor the airspace of a predetermined location using ambient transmissions from at least one uncontrolled transmitter and using initial position information relating to an object approaching the predetermined location. This initial position information may include an electronic or verbal communication of the object""s position at a predetermined time. For example, a plane approaching an airport may provide the system with its position, thereby allowing the system to quickly establish an accurate track for the plane.
In another embodiment, the present invention is used to provide enhanced airspace awareness around a predetermined location as well as enhanced ground-traffic awareness within the predetermined location using ambient transmissions from at least one uncontrolled transmitter.
In another embodiment, the present invention is used to enable a mobile radar system that provides enhanced airspace awareness during a predetermined event using ambient transmissions from at least one uncontrolled transmitter. In a preferred embodiment, the present invention is used as part of a monitoring system in which a vehicle is deployed to a predetermined location to receive ambient transmissions from at least one uncontrolled transmitter.
In yet another embodiment, the present invention is used to select a subset of ambient transmission signals from a plurality of ambient transmission signals based on a set of predetermined criteria.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.